Furnace And Method For Electroslag Remelting

ABSTRACT

The invention relates to a furnace and a method for electroslag remelting, wherein the furnace ( 37 ) comprises a base frame ( 38 ), wherein the base frame comprises supports ( 39 ) which bear a furnace head ( 41 ), wherein at the furnace head, an electrode can be disposed, wherein the electrode can be melted on in a crucible disposed below the furnace head, wherein the furnace comprises a transformer ( 42 ) which can supply electric power for melting on the electrode, wherein the transformer is fixedly disposed at the transformer.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of German Patent Application No. 10 2012 210 281.7 filed on Jun. 19, 2012, which is fully incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The invention relates to a furnace and method for electroslag remelting (ESR), wherein the furnace comprises a base frame, wherein the base frame comprises supports which bear a furnace head, wherein at the furnace head, an electrode can be disposed, wherein the electrode can be melted on in a crucible disposed below the furnace head, wherein the furnace comprises a transformer which can supply electric power for melting on the electrode.

BACKGROUND OF THE INVENTION

With the so-called electroslag remelting process, material electrodes are remelted for producing material blocks, wherein the latter serve as semi-finished products for producing components having a high material quality. With respect to the installations or methods used in this context, so-called sliding crucible installations are distinguished with which the crucibles, in which the blocks generated by burning down the electrode solidify, are provided with a displaceable crucible bottom in order to produce such blocks, so to speak, as a continuous strand. With the so-called stationary crucible method, remelting of the material electrode is effected in a block whose longitudinal dimensions are fixed, wherein the crucible used here is equipped with a fixed crucible bottom. Subsequently, the material electrode is continuously fed to the crucible by means of a feed movement. The feed movement of the material electrode is performed by a furnace head of the furnace in such a manner that the furnace head, at which the material electrode is mounted, can be moved toward the crucible. With sliding crucible installations, too, a movable material electrode is provided on a regular basis. Furthermore, the material electrode can be mounted at a so-called electrode rod, via which the feed movement is effected.

The electric power required for melting on the material electrodes is subsequently supplied by one or more transformers which can transform a high network voltage and a low amperage into a low voltage with a high amperage. For this, multiple transformers can be connected in series in particular, wherein only the last transformer, which is connected to the electrodes, supplies the electric power or the required amperage for melting on the electrode. Said transformers are regularly fixedly installed in a transformer station separate from the furnace or in a room spaced apart and detached from the base frame of the furnace. It is also known to dispose a transformer in such a way on a base frame formed specially for this purpose or on a level of a building, which surrounds the base frame of the furnace, that the transformer is brought closer to the base frame of the furnace. Furthermore, the transformer has a comparatively high weight, which also has to be taken into account when selecting an installation site for the transformer. In particular by means of a room specially formed for the transformer, this can be taken into account.

Furthermore, the transformer which supplies the electric power for melting on the electrode has to be connected to the furnace head by means of a plurality of cables. At the furnace head, the cables are again connected to a contact device which is connected to the electrode and a bottom plate of the crucible or of a generated block in such a way that the electric power can be conducted through the electrode and the block. Here, the contact device can comprise bars or tubes which are disposed coaxially relative to the block and which have a comparatively large cross-section, such that they do not heat up significantly when the electric power is conducted through. Since the furnace head is moved relative to the fixedly installed transformer by means of a potential movement of the electrode, the cables between the transformer and the furnace head have to be formed flexible. In particular, a horizontal movement of the cables is effected when the electrode is exchanged by means of a horizontal swiveling of the furnace head or of the electrode relative to the crucible, and a vertical movement is also possible in this context. In particular with the described horizontal movement, the cables are twisted. Therefore, the cables have a comparatively small cross-section, whereby the cables heat up considerably during operation of the furnace. Therefore, a plurality of cables is used which each feature a coating through which cooling water flows. Apart from high acquisition costs, such water-cooled high-current cables have a number of disadvantages. For instance, the electrical losses are increased by using the flexible high-current cables, which impairs the efficiency of the furnace as a consequence of the higher power consumption. Furthermore, the water-cooled high-current cables are subject to wear and tear due to the relative movement of the base frame and the transformer. The cables can also move on their own due to magnetic fields surrounding the cables and can knock against each other. Therefore, it is necessary to maintain the cables regularly and, if necessary, to exchange them. The same applies for the installation required for cooling the cables.

SUMMARY OF THE INVENTION

The present invention is based on the task to propose a furnace as well as a method for electroslag remelting which can be produced and performed, respectively, in a more cost-effective way.

With the furnace for electroslag remelting (ESR) according to the invention, the furnace comprises a base frame, wherein the base frame has supports which bear a furnace head, wherein at the furnace head, an electrode can be disposed, wherein the electrode can be melted on in a crucible disposed below the furnace head, wherein the furnace comprises a transformer which can supply electric power for melting on the electrode, wherein the transformer is fixedly disposed at the furnace head.

Here, the transformer is in particular defined as a transformer which supplies the electric power with the corresponding amperage which is suitable for melting on the electrode. Disposing the transformer at the furnace head in a fixed manner includes directly disposing the transformer at the furnace head. Consequently, the transformer is disposed in close proximity to the electrode and can also follow a potential movement of the furnace head. Therefore, flexible and consequently necessarily water-cooled high-current cables do not have to be used. A current supply to the furnace head is considerably simplified in this way and the losses caused by the high-current cables are reduced, which results in an improvement in the efficiency of the furnace due to a reduction of the power consumption. Neither is it still necessary to provide a room specially formed for installing the transformer. Although, initially, there are higher costs for forming the base frame since it has to bear the transformer, these costs are outweighed by sparing the high-current cables and by the reduced operating costs. All in all, thus lower investment and operating costs are incurred.

The supports of the base frame can be formed column-shaped and can form at least one bearing plane of the furnace head together with horizontal bearings of the base frame. In this way it becomes possible, by means of horizontal bearings, to form one or more bearing planes which can be walked on by service personnel like levels. Furthermore, devices of the furnace can be formed at the horizontal bearings. Consequently, the furnace head itself can be formed by one or more bearing planes above the crucible.

Thus, it is particularly advantageous if the transformer is fixedly disposed on the bearing plane. Preferably, the transformer can be disposed on the bearing plane via which the electrode and the bottom plate of the crucible are supplied with electric power. Even with a vertical movement of the electrode relative to the transformer, it is not necessary anymore to use flexible cables.

Instead, at the furnace head, a contact device for transmitting the electric power to the electrode, an electrode rod and/or the bottom plate of the crucible can be formed, wherein the transformer can be disposed directly adjacent to the contact device. The contact device can include a sliding contact via which the electric power can be conducted from the transformer directly into the electrode. Alternatively, it is also possible to connect an electrode rod, by means of which the electrode can be mounted at the base frame, to the contact device. Furthermore, the bottom plate of the crucible can be fixedly connected to the contact device via busbars or tubes with a comparatively large cross-section.

The transformer can also be fixedly disposed relative to the contact device. In this way, it is not necessary to form technically complex current conducting devices between the transformer and the contact device.

Subsequently, the transformer can be connected to the contact device by means of a rigid busbar device. For instance, a busbar device formed from simple busbars with a comparatively large cross-section can be produced particularly easily and inexpensively, wherein in this case, a distance of the transformer to the contact device would not even have to be particularly small.

In one embodiment of the furnace, the furnace head for performing the method for electroslag remelting can be formed stationary, and the crucible can have a bottom plate which is movable relative to the furnace head. Here, the electrode could be movably disposed at the furnace head nevertheless.

In contrast, the bottom plate can be formed stationary, and the furnace head can be formed horizontally movable relative to the crucible.

Alternatively, the crucible can have a stationary bottom plate and the furnace head can be formed stationary relative to the bottom plate. When the electrode is melted off, the electrode would then have to be lowered continuously toward the bottom plate. This does not preclude, however, that the electrode can also be movable relative to the furnace head. A relative movability of the electrode with respect to the furnace head, in particular in the horizontal direction, can be required in such cases when the furnace is fitted with the electrode and the latter has to be inserted into the crucible from above, for instance.

The furnace can be a furnace for electroslag remelting under vacuum, under inert gas, under air atmosphere or under pressure. In this way, it becomes possible to use the advantageous disposition of the transformer for different furnaces for electroslag remelting.

With the method for electroslag remelting (ESR) with a furnace according to the invention, the furnace comprises a base frame, wherein the base frame comprises supports which bear a furnace head, wherein at the furnace head, an electrode is disposed, wherein the electrode is melted on in a crucible disposed below the furnace head, wherein the electrode is melted on into the crucible by means of a feed movement of the electrode, wherein the furnace comprises a transformer which supplies electric power for melting on the electrode, wherein the transformer is moved together with the furnace head.

In particular the fact that the transformer is moved together with the furnace head has the advantage that flexible high-current cables are not required. Regarding the advantages resulting therefrom, reference is made to the preceding description of the furnace according to the invention.

Further advantageous embodiments of the device and method arise from the descriptions of the features of the device disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, a preferred embodiment of the invention is described in more detail with reference to the attached drawing.

In the figures:

FIG. 1: shows a furnace for electroslag remelting according to the state of the art in a side view;

FIG. 2: shows a furnace for electroslag remelting according to one embodiment of the invention in a side view.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 shows a furnace 10 for electroslag remelting (ESR) under inert gas according to the state of the art. A base frame 11 forms a bearing plane 12 of a furnace head 13, wherein the bearing plane 12 and the furnace head 13, respectively, are mounted on supports 14. The furnace head 13 comprises a feed drive 15 for an electrode 16 with a spindle 17 and an electrode suspension 18 as well as an electrode rod 19 which connects the electrode 16 to the electrode suspension 18. Furthermore, by means of the base frame 11, two walkable platforms 20 and 21 are formed. Below the furnace head 13, a crucible 22 is disposed in which an ingot 23 and a melting bath 24 are already present. A bottom plate 25 of the crucible 22 is stationarily, that is fixedly, disposed on a base 26. Furthermore, above the crucible 22, a protective gas chamber 27 is formed which makes it possible to melt on the electrode 16 under protective gas. In a separate room 28, which is only illustrated partly here, a transformer 29 for supplying electric power is disposed, which is connected to an installation room 32 for the base frame 11 via a passage opening 30 in a wall 31. In particular, the transformer 29 is connected to the electrode 16 and the crucible 22 by means of water-cooled high-current cables 33 via a contact device 34. For this, busbars 35 are coaxially disposed at the crucible 22. Furthermore, at the electrode rod 19, a sliding contact 36 of the contact device 34 for transmitting the electric power onto the electrode 16 is present. Lowering the electrode 16 into the crucible 22 now works, at least partially, with lowering the electrode suspension 18, such that the electrode 16 is moved relative to the transformer 29. For fitting the furnace head 13 with a new electrode 16, it is necessary to horizontally swivel the base frame 11 relative to the transformer 29. This is effected by means of a pivoting around one of the supports 14, whereby the high-current cables 33 are also twisted.

FIG. 2 shows one embodiment of a furnace 37 for electroslag remelting (ESR) according to the invention. However, in particular neither a crucible nor an electrode is illustrated here. With respect to its essential configuration, the furnace 37 corresponds to the furnace precedingly described in FIG. 1. In contrast, at a base frame 38 of the furnace 37 above supports 39, a bearing plane 40 is formed. On the bearing plane 40 and thus at a furnace head 41 of the furnace 37, a transformer 42 is directly disposed and, via rigid busbars 43 with a comparatively large cross-section, is connected to a contact device 44 which is in turn connected to the electrode not shown here and to the crucible. Thus, the high-current cables known from the state of the art can inexpensively be replaced by simply formed busbars 43. Only by disposing the transformer 42 at the furnace head 41, this becomes possible. 

1. A furnace (37) for electroslag remelting, wherein the furnace comprises a base frame (38), wherein the base frame comprises supports (39) which bear a furnace head (41), wherein at the furnace head, an electrode can be disposed, wherein the electrode can be melted on in a crucible disposed below the furnace head, wherein the furnace comprises a transformer (42) which can supply electric power for melting on the electrode, characterized in that the transformer is fixedly disposed at the furnace head.
 2. The furnace according to claim 1, characterized in that the supports (39) are formed column-shaped and form at least one bearing plane (40) of the furnace head (41) together with horizontal bearings.
 3. The furnace according to claim 1 or 2, characterized in that the transformer (42) is fixedly disposed on the bearing plane (40).
 4. The furnace according to one of the preceding claims, characterized in that at the furnace head (41), a contact device (44) for transmitting the electric power to the electrode, an electrode rod and/or a bottom plate of the crucible is formed, wherein the transformer (42) is disposed directly adjacent to the contact device.
 5. The furnace according to claim 4, characterized in that the transformer (42) is fixedly disposed relative to the contact device (44).
 6. The furnace according to claim 4 or 5, characterized in that the transformer (42) is connected to the contact device (44) by means of a rigid busbar device (43).
 7. The furnace according to one of the preceding claims, characterized in that the furnace head is formed stationary, and the crucible has a bottom plate which is movable relative to the furnace head.
 8. The furnace according to one of the claims 1 to 6, characterized in that the bottom plate is formed stationary, and the furnace head (41) is formed horizontally movable relative to the crucible.
 9. The furnace according to one of the claims 1 to 6, characterized in that the crucible has a stationary bottom plate, and the furnace head is formed stationary relative to the bottom plate.
 10. The furnace according to one of the preceding claims, characterized in that the furnace (37) is configured for electroslag remelting under vacuum, under inert gas, under air atmosphere or under pressure.
 11. A method for electroslag remelting with a furnace (37), wherein the furnace comprises a base frame (38), wherein the base frame comprises supports (39) which bear a furnace head (41), wherein at the furnace head, an electrode is disposed, wherein the electrode is melted on in a crucible disposed below the furnace head, wherein the electrode is melted on into the crucible by means of a feed movement of the electrode, wherein the furnace comprises a transformer (42) which supplies electric power for melting on the electrode, characterized in that the transformer is moved together with the furnace head. 